Atomic / phase data
Reference values and atmospheric abundance are evaluated.
FCC solid
Low-pressure solid argon is FCC.
Emission
Discharge glow is excited-state emission; ordinary gas is colorless.
Geography
Atmospheric occurrence is global/conceptual rather than pinned.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Argon (Ar)
Argon is element 18, a closed-shell noble gas that makes up about 0.94% of Earth’s atmosphere. It is chemically quiet in ordinary conditions yet technologically valuable as a protective gas and spectroscopic plasma.
Argon atomic number, mass, electron configuration and key properties
Argon has 18 protons. A neutral argon atom has 18 electrons; argon-40 has 22 neutrons, while other argon isotopes have different neutron counts.
Argon: quick answers
How many protons, neutrons and electrons does argon have?
Argon’s atomic number is 18, so every argon atom has 18 protons, and a neutral atom also has 18 electrons. Its most common natural isotope, argon-40, has 22 neutrons (other isotopes have different neutron counts).
What is the symbol for argon?
The chemical symbol for argon is Ar.
Is argon a solid, liquid or gas at room temperature?
Argon is a gas at room temperature (about 25 °C).
What family (group) is argon in?
Argon is a noble gas, in group 18, period 3 of the periodic table.
How many valence electrons does argon have?
Argon has 8 valence electrons, the electrons in its outer shell, which matches its position in group 18.
What is the electron configuration of argon?
The ground-state electron configuration of argon is [Ne] 3s² 3p⁶.
From atomic number to chemistry
Read these as a chain of causes, not as isolated facts. Each step links to the concept hub if you want the underlying idea explained.
18 protons define argon.
The ground-state configuration provides the starting point for its chemistry.
Periodic position organizes recurring chemistry and trends.
The teaching nucleus is one isotope, not the relative atomic mass.
Phase boundaries are condition-dependent and evidence-labelled.
Argon in its period and family
Argon is the Period 3 noble gas in Group 18. Its closed valence shell explains very low ordinary chemical reactivity.
Argon Visual Lab
Compare colorless Ar gas with excited emission, inspect the filled 3p shell, freeze an FCC rare-gas lattice and connect atmospheric abundance to air separation, welding and radiogenic ⁴⁰Ar.
Every mark points to one exact feature
The numbered markers explain the same information system used throughout Element Lookup. Unknown or predicted fields remain visibly labelled rather than being replaced with guesses.
Argon in one minute
Atomic number 18 means 18 protons.
Neutral argon has a closed [Ne]3s²3p⁶ shell.
Argon is colorless at ordinary conditions; glow requires excitation.
Argon is about 0.94% of Earth’s atmosphere.
Most atmospheric argon is ⁴⁰Ar, strongly influenced by long-term ⁴⁰K decay in Earth materials.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 8 electrons
The filled 3p orbitals are atomic probability distributions. The visible glow in a discharge comes from excited-state transitions and is not a permanent colored electron cloud.
When frozen under ordinary low-pressure conditions, argon forms an FCC rare-gas crystal held mainly by dispersion forces. The viewer is a conventional-cell teaching schematic.. The viewer is evidence-aware: measured structures are identified as such; unknown bulk structures stay unknown.
Teaching visualization; not a literal finite sample or thermal trajectory.What this model does—and does not—show
The filled 3p orbitals are atomic probability distributions. The visible glow in a discharge comes from excited-state transitions and is not a permanent colored electron cloud.
Where do I meet argon?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Welding shield gas
Argon provides an inert atmosphere that protects hot weld metal from reactive air.
Colorless gas → excited emission → inert shield
Argon’s visible glow is an excited-state phenomenon; the ordinary gas remains colorless and chemically quiet.
Colorless monatomic Ar
Ordinary argon is colorless and monatomic.
Neon, argon and krypton
Compare nearby elements to see which patterns repeat and which properties remain element-specific.
| Boil | 27.104 K |
|---|---|
| Atmosphere | trace |
| Boil | 87.302 K |
|---|---|
| Atmosphere | ~0.94% |
| Boil | 119.735 K |
|---|---|
| Atmosphere | ~1 ppm |
Argon properties: atomic, physical, thermal and chemical
Categories follow the science of this element rather than a fixed decorative template. Each row carries condition/provenance context and an evidence label; unknown values stay unknown.
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Atomic number | 18 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | 39.95 | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Ne] 3s² 3p⁶ | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 18 · Period 3 · p-block | Periodic-table placement | Evaluated |
| Electronegativity | Unknown | Source-reviewed; see Sources below | Unknown |
| Reference isotope | ⁴⁰Ar | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Colorless monatomic gas at 20 °C | Source-reviewed; see Sources below | Evaluated |
| Density | 0.001633 g/cm³ | Source-reviewed; see Sources below | Evaluated |
| Material / molecular structure | Solid argon · face-centred cubic | When frozen under ordinary low-pressure conditions, argon forms an FCC rare-gas crystal held mainly by dispersion forces. The viewer is a conventional-cell teaching schematic. | Measured |
| Classification | Noble gas | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | When frozen under ordinary low-pressure conditions, argon forms an FCC rare-gas crystal held mainly by dispersion forces. The viewer is a conventional-cell teaching schematic. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 83.81 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 87.302 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | At approximately standard pressure, argon is solid below about 83.81 K, liquid from 83.81 to 87.302 K, and gaseous above. The everyday atmospheric state is therefore gas. | Shared phase registry drives the slider, regions and markers. | Evaluated |
| Condition warning | Temperature and pressure define phase behavior; purity/allotropy may matter. | Teaching condition statement | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Common oxidation states | 0 in ordinary elemental chemistry | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | No common stable monatomic ion in ordinary chemistry | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Argon is the Period 3 noble gas in Group 18. Its closed valence shell explains very low ordinary chemical reactivity. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ⁴⁰Ar | Stable · dominant atmospheric isotope | Reference teaching nucleus: 18 protons and 22 neutrons. Much atmospheric ⁴⁰Ar has radiogenic origin from ⁴⁰K decay. | Evaluated |
| ³⁶Ar | Stable natural isotope | A primordial component useful in atmospheric and geochemical studies. | Evaluated |
| ³⁸Ar | Stable natural isotope | A minor stable isotope used in isotope and nuclear-science contexts. | Evaluated |
| Teaching nucleus | ⁴⁰Ar · 18 protons + 22 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | Atomic, phase and atmospheric-abundance data are evaluated/measured. Atmospheric occurrence is shown conceptually because country pins would be scientifically misleading. | Evidence summary for this guide | Reviewed |
| Structure evidence | When frozen under ordinary low-pressure conditions, argon forms an FCC rare-gas crystal held mainly by dispersion forces. The viewer is a conventional-cell teaching schematic. | Measured structure, labelled schematic, prediction or explicit unknown as applicable. | Reviewed |
| Map evidence rule | Real pins are reviewed examples; conceptual layers are used when pins would mislead. | Geography Explorer 2.0 | Reviewed |
| Source set | 3 primary/reference links listed below | Open the Sources section for the actual references. | Reviewed |
Is Argon a solid, liquid or gas? State at temperature
At approximately standard pressure, argon is solid below about 83.81 K, liquid from 83.81 to 87.302 K, and gaseous above. The everyday atmospheric state is therefore gas.
Where on Earth is Argon found or produced?
Who discovered Argon, and when?
Henry Cavendish observed a small residual fraction of air that resisted known reactions.
Lord Rayleigh and William Ramsay identified argon while resolving a density discrepancy between atmospheric and chemically prepared nitrogen.
Spectroscopy confirmed argon as a distinct element and helped establish the noble-gas group.
Argon is produced by cryogenic air separation for welding, metallurgy, lighting, glazing and scientific uses.
From air to industrial argon: high-level separation context
Argon is naturally mixed through Earth’s atmosphere rather than mined from localized ore deposits.
Large air-separation units cool and fractionate air to produce oxygen, nitrogen and argon-rich streams.
Further purification produces argon grades for welding, metallurgy, electronics and scientific systems.
Gas distribution and, where appropriate, recovery systems deliver argon without changing its elemental identity.
What is argon used for?
Welding
Argon shields weld pools and arcs from oxygen, nitrogen and moisture in air.
Protective atmospheres
Manufacturing and metallurgy use argon where chemical inertness is useful.
Lighting & plasma
Argon is used in discharge lamps and plasma systems because excited atoms emit characteristic lines.
Insulating glazing
Argon is used between panes in many insulated windows.
Argon isotopes and natural abundance
⁴⁰Ar
Stable · dominant atmospheric isotopeReference teaching nucleus: 18 protons and 22 neutrons. Much atmospheric ⁴⁰Ar has radiogenic origin from ⁴⁰K decay.
³⁶Ar
Stable natural isotopeA primordial component useful in atmospheric and geochemical studies.
³⁸Ar
Stable natural isotopeA minor stable isotope used in isotope and nuclear-science contexts.
Five-question Argon check
Atomic number?
Valence-shell occupancy?
Ordinary color?
Industrial source?
Solid lattice at low pressure?
Argon questions students commonly ask
Each answer starts with the direct fact, then explains the chemistry, evidence or material context so the result is understandable rather than merely memorized.
How many protons, neutrons and electrons does argon have?
Short answer: Argon has 18 protons. A neutral argon atom has 18 electrons; argon-40 has 22 neutrons.
Argon’s atomic number is 18, so proton count is always 18. Neutrality balances that with 18 electrons. For the isotope argon-40, subtract 18 from its mass number 40 to find 22 neutrons. Other argon isotopes have different neutron counts, so an unspecified argon atom has no single fixed neutron count.
Key point: Protons identify argon; electrons depend on charge and neutrons depend on isotope.
How many valence electrons does argon have?
Short answer: Eight in the 3s²3p⁶ outer shell.
The neutral-atom ground-state reference used on this page is [Ne] 3s² 3p⁶. This is an isolated-atom reference: bonding and ion formation can change which outer electrons are present or chemically active. The listed common oxidation-state context is 0 in ordinary elemental chemistry, which helps connect the atomic configuration to ordinary chemistry without treating electron counting as a single universal rule.
Key point: Electron configuration is a ground-state atomic reference, not a literal picture of every compound.
What is argon used for?
Short answer: Major uses include welding shield gas, protective atmospheres, lighting/plasma systems and insulating glazing.
Welding: Argon shields weld pools and arcs from oxygen, nitrogen and moisture in air. Protective atmospheres: Manufacturing and metallurgy use argon where chemical inertness is useful. Argon’s familiar purple-blue glow is not the ordinary color of the gas. Unexcited argon is colorless; electrical excitation creates line emission from excited atoms.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Is argon a noble gas?
Short answer: Yes. It is the Period 3 member of Group 18.
This guide classifies Argon as a noble gas. Its periodic position is Period 3, p-block, Group 18. Argon is the Period 3 noble gas in Group 18. Its closed valence shell explains very low ordinary chemical reactivity.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
Is argon naturally purple?
Short answer: No. Ordinary argon gas is colorless; visible glow comes from electrical excitation.
Argon’s familiar purple-blue glow is not the ordinary color of the gas. Unexcited argon is colorless; electrical excitation creates line emission from excited atoms. Argon is colorless at ordinary conditions; glow requires excitation.
Key point: Use the direct answer together with the material, isotope and evidence context shown elsewhere on the page.
Where does argon come from industrially?
Short answer: It is separated from air, typically by large cryogenic air-separation systems.
Argon’s familiar purple-blue glow is not the ordinary color of the gas. Unexcited argon is colorless; electrical excitation creates line emission from excited atoms. At approximately standard pressure, argon is solid below about 83.81 K, liquid from 83.81 to 87.302 K, and gaseous above. The everyday atmospheric state is therefore gas.
Key point: Use the direct answer together with the material, isotope and evidence context shown elsewhere on the page.
Scientific sources for Argon
- Royal Society of Chemistry - Argon
- NIST - Atomic Data for Argon
- CIAAW - Argon isotopic/atomic-weight context
Questions to ask next about Argon
A good element lesson should lead to the next useful question, not end after a list of facts.
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